On Tuesday, September 22, 2015 04:34:19 PM Luiz Capitulino wrote: > Hi, Hi,
Please always CC patches related to power management to linux...@vger.kernel.org. Also CCing Len Brown who's the maintainer of the intel_idle driver and Peter Z. > Some archs allow the system administrator to set the > idle thread behavior to spin instead of entering > sleep states. The x86 arch, for example, has a idle= > command-line parameter for this purpose. > > However, the command-line parameter has two problems: > > 1. You have to reboot if you change your mind > 2. This setting affects all system cores > > The second point is relevant for systems where cores > are partitioned into bookkeeping and low-latency cores. > Usually, it's OK for bookkeeping cores to enter deeper > sleep states. It's only the low-latency cores that should > poll when entering idle. This looks like a use case for PM QoS to me rather. You'd need to make it work per-CPU rather than globally, but that really is about asking for minimum latency. > This series adds the following file: > > /sys/devices/system/cpu/cpu_idle > > This file outputs and stores a cpumask of the cores > which will have idle polling behavior. I don't like this interface at all. You have a cpuidle directory per core already, so what's the reason to add an extra mask file really? > This implementation seems to work fine on x86, however > it's RFC because of the following points (for which > feedback is greatly appreciated): > > o I believe this implementation should work for all archs, > but I can't confirm it as my machines and experience is > limited to x86 > > o Some x86 cpufreq drivers explicitly check if idle=poll > was passed. Does anyone know if this is an optmization > or is there actually a conflict between idle=poll and > driver operation? idle=poll is used as a workaround for platform defects on some systems IIRC. > o This series maintains cpu_idle_poll_ctrl() semantics > which led to a more complex implementation. That is, today > cpu_idle_poll_ctrl() increments or decrements a counter. > A lot of arch code seems to count on this semantic, where > cpu_idle_poll_ctrl(enable or false) calls have to match to > enable or disable idle polling > > Luiz Capitulino (3): > sched/idle: cpu_idle_poll(): drop unused return code > sched/idle: make cpu_idle_force_poll per-cpu > sched/idle: run-time support for setting idle polling > > drivers/base/cpu.c | 44 ++++++++++++++++++++++++ > include/linux/cpu.h | 2 ++ > kernel/sched/idle.c | 96 > +++++++++++++++++++++++++++++++++++++++++++++-------- > 3 files changed, 129 insertions(+), 13 deletions(-) Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
